1. Field of the Invention
The invention relates to a machine tool that includes a fixture that positions a workpiece using hydraulic pressure.
2. Discussion of Background
A machine tool machines a workpiece fixed to a table using a machining fixture. When workpieces having different shapes are machined by such a machine tool, a changeover of a fixture such as a work clamp is required due to changes of workpieces, which may take a long time. Then, Publication No. US2005/179188 describes a fixture in which a fixture plate having a work clamp is fastened by bolts to a fixture base fixed to a table. With the above configuration, a changeover of a fixture is simplified to reduce the time required to change workpieces.
However, when the fixture plate is fastened by bolts to the fixture base, the time to loosen a plurality of bolts, replace the fixture plates, and tighten the bolts again is required at the time of a changeover of the fixture. In addition, when work for fastening the bolts is manually performed, there is a concern about a decrease in machining accuracy, or the like, due to uneven tightening torque of each bolt.
In addition, when manual operation is required for a changeover of the fixture, usually, the machine tool is stopped for safety. Therefore, a power source such as a hydraulic pump cannot be used, and the fixture plate is fastened by bolts in the fixture as described above. Therefore, a long time may be required for a changeover of the fixture.